Condensed-phase versus gas-phase ozonolysis of catechol: A combined experimental and theoretical study

Barnum, Timothy J.; Medeiros, Nicholas J.; Hinrichs, Ryan Z.

doi:10.1016/j.atmosenv.2012.02.019

Cited by 32 publications

(62 citation statements)

References 20 publications

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“…In MNC, both –OH groups are ortho to one another and –NO 2 and –CH 3 are para to the two –OH groups, resulting in preferred OH radical addition at those positions. However, if water complexes with the catechol –OH groups [ Barnum et al , ], then the increased steric hindrance of the R–C–OH groups could impede electrophilic OH radical addition and thus further suppress OH radical uptake at higher RH.…”

Section: Resultsmentioning

confidence: 99%

Multiphase OH oxidation kinetics of organic aerosol: The role of particle phase state and relative humidity

Slade

Knopf

2014

Geophysical Research Letters

160

219

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Organic aerosol can exhibit different phase states in response to changes in relative humidity (RH), thereby influencing heterogeneous reaction rates with trace gas species. OH radical uptake by laboratory‐generated levoglucosan and methyl‐nitrocatechol particles, serving as surrogates for biomass burning aerosol, is determined as a function of RH. Increasing RH lowers the viscosity of amorphous levoglucosan aerosol particles enabling enhanced OH uptake. Conversely, OH uptake by methyl‐nitrocatechol aerosol particles is suppressed at higher RH as a result of competitive coadsorption of H2O that occupies reactive sites. This is shown to have substantial impacts on organic aerosol lifetimes with respect to OH oxidation. The results emphasize the importance of organic aerosol phase state to accurately describe the multiphase chemical kinetics and thus chemical aging process in atmospheric models to better represent the evolution of organic aerosol and its role in air quality and climate.

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Section: Resultsmentioning

confidence: 99%

Multiphase OH oxidation kinetics of organic aerosol: The role of particle phase state and relative humidity

Slade

Knopf

2014

Geophysical Research Letters

160

219

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“…Similar humidity-independent results were observed for the heterogeneous ozonolysis of liquid oleic acid, linoleic acid, and linolenic acid films . Barnum et al (2012) found that higher humidities increased the reactive uptake coefficients for the heterogeneous ozonolysis of thin film solid crystalline catechol as a result of hydrogen bonding interactions between adsorbed water and the diol. A similar effect is probably not operative in the current systems since the methoxyphenol binding interactions with the substrates outweigh interactions with co-adsorbed water.…”

Section: Impact Of Relative Humiditymentioning

confidence: 96%

“…Knopf et al (2011) measured γ = 8.3 × 10 −5 for O 3 on thin film nitroguaiacol, almost three orders of magnitude faster than the current estimate. Barnum et al (2012) found thin film crystalline catechol to have γ = 5.6×10 −5 at 81 % relative humidity. These differences may be due in part to the diffusion of ozone several layers into the solid thin films allowing for reaction with subsurface compounds.…”

Section: Eugenol and Isoeugenol + Omentioning

confidence: 99%

Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

O'Neill

Kawam

et al. 2014

Atmos. Chem. Phys.

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Abstract. Lignin pyrolysis products, which include a variety of substituted methoxyphenols, constitute a major component of organics released by biomass combustion, and may play a central role in the formation of atmospheric brown carbon. Understanding the atmospheric fate of these compounds upon exposure to trace gases is therefore critical to predicting the chemical and physical properties of biomass burning aerosol. We used diffuse reflectance infrared spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol, eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates. Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of 3 × 1018 molecules m−2. The subsequent dark heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic ring between the methoxy and phenol groups with the product conclusively identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and isoeugenol dark ozonolysis also suggested the formation of ring-cleaved products, although ozonolysis of the unsaturated substituent groups forming carboxylic acids and aldehydes was an order of magnitude faster. Average uptake coefficients for NaCl-adsorbed methoxyphenols were γ = 2.3 (± 0.8) × 10−7 and 2 (± 1) × 10−6 for ozonolysis of the aromatic ring and the unsaturated side chain, respectively, and reactions on α-Al2O3 were approximately two times slower. UV–visible radiation (λ > 300 nm) enhanced eugenol ozonolysis of the aromatic ring by a factor of 4(± 1) but had no effect on ozonolysis of the alkene side chain.

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“…Catechol, 1,2-diihydroxybenzene, is widely found in biomass-burning emissions. While catechol was previously thought to primarily undergo ring-opening reactions when exposed to ozone [136], the application of OESI-MS resolved the simultaneous contribution to oxidation by an indirect electron transfer-initiated oxidation, providing HO • radicals [60]. In addition to observing common catechol ozonolysis products [137], it was proposed, for the first time, that oxidation by HO • caused the production of polyhydroxylated aromatic compounds and quinones in atmospheric particles [60].…”

Section: Environmental Information From Laboratory Studies Of Heterogmentioning

confidence: 99%

“…These approaches typically capture the variations in composition in the early stages of aging, but are not necessarily representative of the extended aging periods experienced during transport [61]. More recently, thin films have been used to simulate relevant reactions on the aerosol surface modeling the air-particle interface [61,116,136,143]. This approach has proven quite useful to monitor the degradation of the proxy materials and evolution of condensed and gas phase products in gas cells or environmental chambers [144].…”

Section: Environmental Information From Laboratory Studies Of Heterogmentioning

confidence: 99%

An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

Pillar-Little

Guzmán

2018

Environments

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Due to the adverse effect of atmospheric aerosols on public health and their ability to affect climate, extensive research has been undertaken in recent decades to understand their sources and sinks, as well as to study their physical and chemical properties. Atmospheric aerosols are important players in the Earth’s radiative budget, affecting incoming and outgoing solar radiation through absorption and scattering by direct and indirect means. While the cooling properties of pure inorganic aerosols are relatively well understood, the impact of organic aerosols on the radiative budget is unclear. Additionally, organic aerosols are transformed through chemical reactions during atmospheric transport. The resulting complex mixture of organic aerosol has variable physical and chemical properties that contribute further to the uncertainty of these species modifying the radiative budget. Correlations between oxidative processing and increased absorptivity, hygroscopicity, and cloud condensation nuclei activity have been observed, but the mechanisms behind these phenomena have remained unexplored. Herein, we review environmentally relevant heterogeneous mechanisms occurring on interfaces that contribute to the processing of aerosols. Recent laboratory studies exploring processes at the aerosol–air interface are highlighted as capable of generating the complexity observed in the environment. Furthermore, a variety of laboratory methods developed specifically to study these processes under environmentally relevant conditions are introduced. Remarkably, the heterogeneous mechanisms presented might neither be feasible in the gas phase nor in the bulk particle phase of aerosols at the fast rates enabled on interfaces. In conclusion, these surface mechanisms are important to better understand how organic aerosols are transformed in the atmosphere affecting the environment.

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Condensed-phase versus gas-phase ozonolysis of catechol: A combined experimental and theoretical study

Cited by 32 publications

References 20 publications

Multiphase OH oxidation kinetics of organic aerosol: The role of particle phase state and relative humidity

Multiphase OH oxidation kinetics of organic aerosol: The role of particle phase state and relative humidity

Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation

An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

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